How Good Are Teleconverters? A Non-Technical Look

So I've often wondered if it made more sense to get a really good 200mm or 300mm lens, and then slap a teleconverter on it to get that extra reach. After all, it would save thousands of dollars, and if the starting lens had a nice wide aperture, it would give you the same numbers in the end. I read reviews, I attempted to look at sample images, but I just couldn't see what the sites were saying. The images looked good to me. I didn't see sharpness falling off dramatically as you moved away from the center, I didn't see issues in the corners.

The 70-200mm f/2.8 is all-metal and surprisingly heavy.
First shots with it were canted due to the surprising weight!

Fortunately, I am able to easily rent lenses and various components, so Itested Nikon's 1.4, 1.7, and 2.0 teleconverters on Nikon's 70-200mm f/2.8 VR lens (not the current VR II) with the racing ponies at Pimlico. Where better to test focusing and sharpness? So, now, without a further adieu, images and commentary based on a photography enthusiast's images, not highly calibrated lens test diagrams.

Baseline: This is how good the lens is, on its own
1/3200 at 82mm f/2.8 ISO200

The Teleconverters and Sharpness

Now I went for a little extra reach, mounting the 1.4x. The nice thing is, the autofocus system for the 70-200mm still works!

It is clear that the lens is losing a little something. Not much, but a little. Compare the original image on the left with the crop on the right. Even I can appreciate the ever so slight softness in the horse on the right. Remember, we're losing a couple of stops and the maximum aperture is now smaller.
1/4000 at 280mm f/4 ISO800



Now we move up to the 1.7x and it gets very apparent that you're beginning to really lose something in the image. But that's only if I'm cropping and zooming. At full size, the image looks brilliant. Again, at wide open and with the 1.7x, we're closing the aperture more.
1/3200 at 340mm f/4.8 ISO640



Now we go to the 2.0x teleconverter, and start losing some serious light. I decided to give zoomed in views of the corners on this one, so that the sharpness can be really appreciated. I don't know how, but the 2.0x just looks good.
1/2500 at 210mm f/5.6 ISO1600

The main image.


Upper right corner. You can really see the detail in the horse blanket, and it is fairly crisp. This surprised me.


Now to the lower right corner. Here you can see the details on the boots, but they do become a little fuzzier as you move further from the center.


Lower left corner. This is the shot that showcases the loss of sharpness when using the 2.0x. The coat on the legs has become blurry, but still detailed enough to pick out the hairs.


Upper left corner. This one vexes me. The coat is very similar to the lower left shot, save for the extreme upper left corner. The top of the horses hindquarter is full of detail and is quite crisp. VERY surprising.

Focusing Speed

But what about lens performance in the areas that you may not know about until you experience them for yourself, like focus speed? This is where the Nikon teleconverters blew me away. The 70-200mm lens is a fast focusing lens in my opinion. I expected to lose some serious performance, and probably lose some good action shots as a result. Boy was I wrong. I missed the shot on the left. But the next image, taken while the horses were still in the same stride? Boom. SHARP. It may be a slower focusing speed than the lens without the teleconverter, but that is fast enough for me.
1/2500 at 400mm f/5.6 ISO1600



And one final image with commentary, all the way out at full stretch, with the focus point (and subject matter) fully off center. I won't lie. The detail looks pretty freakin' good!
1/3200 at 400mm f/5.6 ISO1250

Equipment Used

Nikon D7100 Camera
70-200mm f/2.8 VR lens
Nikon 1.4x Teleconverter
Nikon 1.7x Teleconverter
Nikon 2.0x Teleconverter


Images